Travel in Oceania / Tahiti

I have two weeks in November/December to travel Oceania (Fiji, Marshall
Islands, Cook Islands, Micronesia, etc.) and need some opinions. I was
originally going to spend the time in Hawaii, but everyone goes to Hawaii,
so I thought I would go one step further.

What I am looking for is a tropical paradise with my own
islands/atolls/reefs to explore. Preferably I would like to be able to rent
a small boat and go from island to uninhabited island and just imagine what
it would be like having to live on a "deserted island". I want to soak up
the culture, yet live out my explorer/adventurer side.

I like the fact that Fiji has some large hills/mountains where I can hike,
but I don't know anything about it (yes I have read many websites and picked
up countless brochures). I don't want to stay in a posh resort the whole
time, although one or two nights coudlnt heart! I also was thinking about
the Marshall Islands because of the nuclear testing historical aspect, as
well as amazing diving, although I don't plan on going on any decompression
dives.

So those that have traveled to this part of the world, what is your opinion?
Should I spend the extra money to get to the Marshall or Cook Islands?
Should I stick with Fiji or Tahiti and find a side tour once I am there?
What about renting a boat and hitting up the reefs and small islands for
snorkeling and such?

Any help appreciated, I have almost exhausted traditional research methods.

Thanks,
Tim